Hi All,
While having a basic understanding of how routing stuff works I don't seem to be able get my head around this one.
I have a branch router with 2 FE interfaces connected like this:
FE0/0 ---> WAN access device (192.168.1.105) FE0/1 ---> LAN (192.168.1/24)
Then relevant configuration is like this:
interface FastEthernet0/0 ip address 192.168.1.1 255.255.255.0 duplex auto speed auto
interface FastEthernet0/1 no ip address duplex auto speed auto
interface FastEthernet0/1.1 encapsulation dot1Q 1 native ip unnumbered FastEthernet0/0
ip route 0.0.0.0 0.0.0.0 192.168.1.105 ip route 192.168.1.105 255.255.255.255 FastEthernet0/1.1
When the las t route is not present the WAN cannot be reached. Why is it needed? I can see some VLAN config on FE0/1.1. Is it really needed?
In general how does this work? show ip route shows:
ip route 0.0.0.0 0.0.0.0 192.168.1.105 ip route 192.168.1.105 255.255.255.255 FastEthernet0/1.1
Here is how I (don't) understand it. Say a packet arrives at FE0/1.1 for some WAN destination. Then it is forwarded to 192.168.1.105 as per default route. But there is a host route which puts this packet through FE0/1.1. So how does it reach the WAN if it is phisically connected to FE0/0 and not to FE0/1?? More, why this packet does not reach the WAN if not forced through the (wrong) phisical interface?
And last. Why should such a setup be preferable over a simpler one like:
interface FastEthernet0/0 ip address 192.168.1.1 255.255.255.0 duplex auto speed auto
interface FastEthernet0/1 ip address 192.168.1.2 255.255.255.0 duplex auto speed auto
ip route 0.0.0.0 0.0.0.0 192.168.1.105 ip route 192.168.1.105 255.255.255.255 FastEthernet0/0 ip route 192.168.1.0 255.255.255.0 FastEthernet0/1
Thanks in advance!